1. Field of the Invention
The present invention relates to a triarylamine derivative having absorption in a near infrared region.
2. Description of the Related Art
Conventionally, a diimmonium compound which is one kind of triarylamine derivative has been widely known as a near infrared absorbing compound (see, for example, Japanese Patent Application Laid Open (JP-A) No. 4-146905; JP-A No. 5-142811; JP-A No. 2002-82219; “Der Deutschen Chemischen Gesellschaft” vol. 92, pp. 245-251 (1959); and “Spectrochemica Acta” vol. 23, pp. 655-675 (1967)), and has been widely used in photopolymerization initiators, and electrophotographic photoreceptors. However, generally, the diimmonium compound as a near infrared absorbing compound still has a problem in wet heat resistance and solubility. On the other hand, it is known that wet heat resistance and solubility can be improved by changing an anion which is a counterion, or changing an alkyl group bound to an aminophenyl group of a diimmonium ion (see, for example, JP-A No. 2005-325292, JP-A No. 2005-336150 and JP-A No. 2006-143674).
In addition, it is known that heat resistance is improved by using an antimony hexafluoride ion as a counterion of the diimmonium compound. However, since a compound containing antimony is a deleterious substance, in view of loading on the environment, a high heat resistant diimmonium compound containing no antimony is desired in the industrial field. As a means to solve this problem, a diimmonium compound having a counterion such as a perchlorate ion or a hexafluorophosphate ion is known.